Downsides to Desalination

Throwing salt over your shoulder after you spill some, is a ritual that originated in ancient Rome. Back then, salt was a very precious and expensive commodity. To carelessly lose any was considered a bad omen. To rectify this terrible error, you needed to lose some of what you valued most. Times have changed and now we have an overabundance of salt. Instead of throwing it over our shoulder to make up for misdeeds, we may be looking over our shoulder to make sure were are not caught dumping it.

As water quality continues to diminish around the world, advocates are promoting desalination as a technological solution. They point to the earth’s abundant water supplies, such as the ocean or brackish aquifers, which desalination can treat to provide another source of drinking water. Yet, these advocates tend to gloss over the environmental impacts of the concentrated salt waste that is produced.

Desalination works by removing salts and minerals from water supplies, generally using sophisticated membrane technology which is very energy intensive and quite costly. This technique not only results in producing freshwater, it also generates a concentrated brine which needs to be disposed of. In some ways, you could say desalination is just another version of “robbing Peter to pay Paul.” In the end, you still have the problem of too much salt.

Unfortunately, there is no sound way to handle the concentrated brine waste produced. Currently, many countries with coastal desalination facilities release the brine waste back into the ocean. A practice which marine biologists warn is taking a heavy toll on the ocean’s health.

In a Scientific American online article, Jeffrey Graham of the Scripps Institute of Oceanography’s Center for Marine Biotechnology and Biomedicine, noted that the highly concentrated salt waste from desalination processes “can wreak havoc on marine ecosystems.” He expressed concern that “the disappearance of some organisms from discharge areas may be related to the salty outflow.”

The same article discusses how the seawater intake process can also be detrimental to biodiversity. Desalination plants essentially vacuum up sea water through intake pipes and “inadvertently kill millions of plankton, fish eggs, fish larvae and other microbial organisms that constitute the base layer of the marine food chain.” This reduces the amount of food available for larger ocean creatures.

Some desalination supporters suggest injecting the concentrated brine deep into the ground, where it, presumably, will do no harm. However, Menachem Elimelech, a Professor at the Yale University School of Engineering and Applied Science, doesn’t believe that solution would be sustainable. In a Deutsche Wells online article, Elimelech states “If you have many many desalination plants injecting this salt into the groundwater, it may affect the groundwater 50, 100 or 500 years from now.”

Being a water resources junkie, I couldn’t agree more. Water doesn’t stay in one place and it’s impossible for us to know the exact nature of any formation that the liquid waste is pumped into. Fractures, fissures, and faults might be unseen pathways for this solution to eventually move into and contaminate productive aquifers. Why take the chance?

Also, consider the intake material from the ocean is not just water and salt but also organic matter, bacteria, and other materials. All these substances must be treated and removed before the sea water is run through the reverse osmosis membranes. William Phillip from the University of Notre Dame in Indiana, points out in the Deutsche Wells article that “In order to keep the membranes from clogging up with particles, the sea water has to be treated with chemicals before it is desalinated. These chemicals are then poured back into the sea.”

As the membranes do their job of removing minerals and salts, they gradually get clogged up, making them less efficient. This is where desalination starts to get expensive. It takes a lot of energy to keep pushing water molecules through the reverse osmosis membranes especially when they are blocked by other elements.

Desalination also produces three times the CO2 emissions of conventional water treatment systems. In a world struggling to come to its senses over climate change, adding more greenhouse gases to the atmosphere may not be the best solution. In a way, it may be like rubbing salt into our collective wounds.